diff --git a/lib/os/mpsc_pbuf.c b/lib/os/mpsc_pbuf.c
index bdd7010b128c05..06eb5d92338c7e 100644
--- a/lib/os/mpsc_pbuf.c
+++ b/lib/os/mpsc_pbuf.c
@@ -373,7 +373,7 @@ union mpsc_pbuf_generic *mpsc_pbuf_alloc(struct mpsc_pbuf_buffer *buffer,
 			add_skip_item(buffer, free_wlen);
 			cont = true;
 		} else if (IS_ENABLED(CONFIG_MULTITHREADING) && !K_TIMEOUT_EQ(timeout, K_NO_WAIT) &&
-			   !k_is_in_isr()) {
+			   !k_is_in_isr() && arch_irq_unlocked(key.key)) {
 			int err;
 
 			k_spin_unlock(&buffer->lock, key);
diff --git a/tests/lib/mpsc_pbuf/src/main.c b/tests/lib/mpsc_pbuf/src/main.c
index 201eced47f9e76..923050b1b6d42e 100644
--- a/tests/lib/mpsc_pbuf/src/main.c
+++ b/tests/lib/mpsc_pbuf/src/main.c
@@ -1294,5 +1294,28 @@ ZTEST(log_buffer, test_utilization)
 	zassert_true(packet == NULL);
 }
 
+/* Make sure that `mpsc_pbuf_alloc()` works in spinlock-held context when buf is not available */
+ZTEST(log_buffer, test_alloc_in_spinlock)
+{
+	struct mpsc_pbuf_buffer buffer;
+	struct test_data_var *packet;
+	struct k_spinlock l = {0};
+
+	init(&buffer, 32, false);
+
+	/* Allocate all available buffer */
+	packet = (struct test_data_var *)mpsc_pbuf_alloc(
+		&buffer, 32, K_MSEC(10));
+	zassert_not_null(packet);
+
+	K_SPINLOCK(&l) {
+		/* Try to allocate another buf */
+		packet = (struct test_data_var *)mpsc_pbuf_alloc(
+			&buffer, 32, K_MSEC(10));
+		/* No buf is available this time */
+		zassert_is_null(packet);
+	}
+}
+
 /*test case main entry*/
 ZTEST_SUITE(log_buffer, NULL, NULL, NULL, NULL, NULL);